/**
 * Definition for singly-linked list.
 * struct ListNode {
 *     int val;
 *     ListNode *next;
 *     ListNode(int x) : val(x), next(NULL) {}
 * };
 */
class Solution
{
public:
    bool hasCycle(ListNode *head)
    {
        ListNode *slow = head;
        ListNode *fast = head;
        while (fast != nullptr && fast->next != nullptr)
        {
            fast = fast->next->next;
            slow = slow->next;
            if (fast == slow)
            {
                return true;
            }
        }
        return false;
    }

    bool hasCycle114514(ListNode *head)
    {
        ListNode *cur = head;
        while (cur != nullptr)
        {
            if (cur->val == 114514)
            {
                return true;
            }
            else
            {
                cur->val = 114514;
            }
            cur = cur->next;
        }
        return false;
    }
};